Re: Math expression evaluation error?

[jdh <dhenman@xxxxxxxxx>]

Thanks for the detailed explanation.   I suggest that the an additional 
line be added to the manual, which would say something like:

"   Caution:  The evaluation of an expression is taken a term at a time 
and if there are mixed terms , say integer only and  float terms , the 
integer only ones will not be promoted to real values and the result of 
the whole expression would be an error to common standards. One can use 
the -f option or the  FORCE_FLOAT environment variable to change this 
behavior."

I apologize if this is in the manual already.

Regards.

On 2015年01月09日 12:15, Peter Stephenson wrote:
> On Fri, 09 Jan 2015 11:46:44 -0800
> jdh <dhenman@xxxxxxxxx> wrote:
> > I believe I read that math expression evaluation will convert all
> > calculations in an expression if "any" value in that expression is a
> > real value.
> This isn't the case and wherever this came from needs correcting.
> Please instead read the documentation under ARITHMETIC EVALUATION in the
> zshmisc manual for what actually happens and let us if know if you think
> that is inadequate.  The actually phrasing is "Promotion of integer to
> floating point values is performed where necessary".  It also refers
> above that to C --- there's an underlying assumption here that the user
> has some idea of the operation of C-like languages, which might of
> course not be the case.  "Where necessary" is in general where an
> operator has a floating point number as one argument and an integer as
> another; a C programmer would recognise the use of the word "promotion"
> as implying this, a general user probably not.  So the wording could
> probably be improved.  Brief and to the point suggestions on this from
> anyone are welcome (long rambles on why anyone doesn't understand it
> may be invigorating for the rambler but are less useful to us as
> developers :-)).
>
> See also the following shell option:
>
> FORCE_FLOAT
>         Constants in arithmetic evaluation will be treated  as  floating
>         point  even without the use of a decimal point.  Integers in any
>         base will be converted.
>
> This is most useful in zcalc, which actually has an option for this.
>
>         If the option `-f' is set, all numbers are treated  as  floating
>         point,  hence for example the expression `3/4' evaluates to 0.75
>         rather than 0.  Options must appear in separate words.
>
> pws